This invention relates to a computer printer and means to properly guide Z-fold computer paper therein. More particularly the invention is directed to a paper retainer which allows Z-fold paper to pass into and out of the printer in a normal printing mode of operation and also allows for a Z-fold paper reverse mode of transport to allow re-insertion of the sheets into the printer in a reverse mode of operation for a subsequent second pass through the platen/printer interface.
In certain prior art computer printers or integrators, the Z-fold paper flow basically is unidirectional, namely it is transported from a paper supply bin or box to a printer platen where a print carriage of the jet type or thermal or laser type imprints data on the obverse side of Z-fold sheets. The printed-on sheets then exit from the printer carriage and platen and are folded into a printed-on paper bin or onto a folding surface. If it is necessary to have a capability which permits a user to hand guide the Z-fold paper so that the paper sheets exit to the front of the printer, i.e., drape over the keyboard and extend to the floor below a support table, it is necessary to reverse the paper drive so that the paper is pulled back into the printer and when placed in the forward mode of operation so that the paper can be overprinted with additional printed data. However, when the paper is reintroduced into the platen in a reverse mode of operation the sharp crease of the returning Z-fold paper can become wedged on a normally employed paper tear bar adjacent to the platen. This bar is included on prior art machines to guide the Z-fold paper rearwardly after it has been printed on and also to aid in ripping off one or more sheets from the stack of sheets along a rear relatively sharp edge of the tear bar. As a result of the wedging the paper traction drive becomes jammed stopping the printer. Further, Z-fold paper may rip or becomes partially torn making it difficult to re-feed the Z-fold paper back through the platen area toward the new paper storage bin. The wedging phenomenon is particularly apparent when a considerable weight of paper, such as multiple sheets extending to a floor, is being passed back through the platen.